Single wafer dryer and drying methods

ABSTRACT

In a first aspect, a first method of drying a substrate is provided. The first method includes the steps of (1) lifting a substrate through an air/fluid interface at a first rate; (2) directing a drying vapor at the air/fluid interface during lifting of the substrate; and (3) while a portion of the substrate remains in the air/fluid interface, reducing a rate at which a remainder of the substrate is lifted through the air/fluid interface to a second rate. The drying vapor may form an angle of about 23° with the air/fluid interface and/or the second rate may be about 2.5 mm/sec.

The present application is a continuation-in-part of and claims priorityfrom U.S. patent application Ser. No. 10/286,404, filed Nov. 1, 2002,which claims priority from U.S. Provisional Patent Application Ser. No.60/335,335, filed Nov. 2, 2001. The present application also claimspriority from U.S. Provisional Patent Application Ser. No. 60/542,960,filed Feb. 9, 2004. All of the above patent applications are herebyincorporated by reference herein in their entirety.

FIELD OF THE INVENTION

This invention is concerned with semiconductor manufacturing and is moreparticularly concerned with techniques for drying a substrate.

BACKGROUND OF THE INVENTION

As semiconductor device geometries continue to decrease, the importanceof ultra clean processing increases. Aqueous cleaning within a tank offluid (or a bath) followed by a rinsing bath (e.g., within a separatetank, or by replacing the cleaning tank fluid) achieves desirablecleaning levels. After removal from the rinsing bath, absent use of adrying apparatus, the bath fluid would evaporate from the substrate'ssurface causing streaking, spotting and/or leaving bath residue on thesurface of the substrate. Such streaking, spotting and residue can causesubsequent device failure. Accordingly, much attention has been directedto improved methods for drying a substrate as it is removed from anaqueous bath.

A method known as Marangoni drying creates a surface tension gradient toinduce bath fluid to flow from the substrate in a manner that leaves thesubstrate virtually free of bath fluid, and thus may avoid streaking,spotting and residue marks. Specifically, during Marangoni drying asolvent miscible with the bath fluid (e.g., IPA vapor) is introduced toa fluid meniscus which forms as the substrate is lifted from the bath oras the bath fluid is drained past the substrate. The solvent vapor isabsorbed along the surface of the fluid, with the concentration of theabsorbed vapor being higher at the tip of the meniscus. The higherconcentration of absorbed vapor causes surface tension to be lower atthe tip of the meniscus than in the bulk of the bath fluid, causing bathfluid to flow from the drying meniscus toward the bulk bath fluid. Sucha flow is known as a “Marangoni” flow, and can be employed to achievesubstrate drying without leaving streaks, spotting or bath residue onthe substrate.

SUMMARY OF THE INVENTION

In a first aspect of the invention, a first method of drying a substrateis provided. The first method includes the steps of (1) lifting asubstrate through an air/fluid interface at a first rate; (2) directinga drying vapor at the air/fluid interface during lifting of thesubstrate; and (3) while a portion of the substrate remains in theair/fluid interface, reducing a rate at which a remainder of thesubstrate is lifted through the air/fluid interface to a second rate.The drying vapor may form an angle of about 23° with the air/fluidinterface and/or the second rate may be about 2.5 mm/sec.

In a second aspect of the invention, a second method of drying asubstrate is provided. The second method includes the steps of (1)lifting a substrate through an air/fluid interface; and (2) whilelifting the substrate, directing an isopropyl alcohol vapor at theair/fluid interface. The isopropyl alcohol vapor is delivered using acarrier gas and the isopropyl alcohol vapor has a concentration of about1.5% within the carrier gas.

In a third aspect of the invention, a first method of semiconductordevice manufacturing is provided that includes the steps of (1) loweringa substrate through a loadport into a processing portion of a chamber;(2) rotating the substrate from a first orientation wherein thesubstrate is in line with the loadport to a second orientation whereinthe substrate is in line with an unload port, horizontally displacedfrom the loadport; and (3) raising the substrate out of the processingportion at the unload port. The method may further include the steps ofrefreshing fluid in the chamber by employing a deionized water orcleaning chemistry flow rate of about 1.3 liters/minute ±20% and/orspraying deionized water or the cleaning chemistry at the substrate at aflow rate of about 2.5 liters/minute ±20%.

In a fourth aspect of the invention, a second method of semiconductordevice manufacturing is provided that includes the steps of (1) loweringa substrate through a loadport into a processing portion of a chamber;(2) rotating the substrate from a first orientation wherein thesubstrate is in line with the loadport to a second orientation whereinthe substrate is in line with an unload port, horizontally displacedfrom the loadport; (3) raising the substrate out of the processingportion through a rinsing section of the processing portion; and (4)causing the substrate to dwell in the rinsing section for a time period.Numerous other aspects are provided.

Other features and aspects of the present invention will become morefully apparent from the following detailed description, the appendedclaims and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic side view of an inventive drying apparatuscomprising a processing portion, and an output portion, both configuredaccording to a first aspect;

FIGS. 2A-I are schematic side views of the inventive drying apparatus ofFIG. 1 showing sequential stages of wafer transport through, and outputfrom, the inventive drying apparatus;

FIGS. 3A-B are a schematic side view and a top plan view respectivelyshowing the drying apparatus of FIG. 1 wherein the output portion isconfigured according to a second aspect;

FIGS. 4A-I are schematic side views of the inventive drying apparatus ofFIGS. 3A-B showing sequential positions of the output portion duringwafer output thereto;

FIG. 5 is a schematic side view showing the inventive drying apparatuswherein the processing portion is configured according to a secondaspect;

FIG. 6 is a schematic side view of a vapor flow deflector that may beinstalled in association with a vapor nozzle in a drying apparatus;

FIG. 7 is a graph which plots the number of particles observed on wafersdried via various IPA concentrations and various flow rates;

FIG. 8A is a schematic drawing useful in describing a vapor flow angle;and

FIG. 8B is a table showing preferred vapor flow angles for dryingsubstrates comprising various materials.

DETAILED DESCRIPTION

A drying apparatus provided in accordance with the present inventioncomprises a processing portion and an output portion. The processingportion includes a main chamber that may be configured according to twomain aspects. A first aspect (submersion chamber 18 a) submerges a waferin a bath of fluid and is shown and described with reference to FIGS.1-2I; a second aspect (spray chamber 18 b) sprays an unsubmerged waferwith fluid and is shown and described with reference to FIG. 5.

Similarly, the output portion includes an output platform that may beconfigured according to two main aspects. A first aspect (rotationplatform 58) rotates a wafer from a generally vertical orientation to agenerally horizontal orientation and is shown and described withreference to FIGS. 1-2I; a second aspect (translation platform 158)translates horizontally so as to receive a generally vertically orientedwafer in one of a plurality of wafer receivers, and is shown anddescribed with reference to FIGS. 3A-4K.

Each aspect of the processing portion and output portion is consideredinventive on its own. Accordingly, each aspect of the processing portionmay be used with either aspect of the output portion, and vice versa.Additionally each aspect of the processing portion and the outputportion may be used with conventional output portions and processingportions, respectively. Finally, numerous individual features of theprocessing portions and output portions are inventive, as will beapparent with reference to the figures and the description that follows.

FIG. 1 is a side schematic view of an inventive drying apparatus 11 inwhich the processing portion and the output portion are configuredaccording to a first aspect of the present invention. The inventivedrying apparatus 11 comprises a processing portion 10 and an outputportion 12.

Processing Portion—First Aspect

The processing portion 10 comprises a submersion chamber 18 a whichsubmerges a wafer in a bath of fluid, such as deionized water, and whichmay or may not include a surfactant, or other cleaning chemistry such asApplied Materials' ElectraClean™ solution.

An upper separation wall 24 (FIG. 2A) divides the submersion chamber 18a into two sections: a rinsing section 26 and a “drying” section 28. Byseparating the drying section 28 from the rinsing section 26, a cleanerexit zone is maintained and the risk of removed particles re-adhering tothe wafer during drying is reduced, as particles tend to be removed inthe rinsing section 26 and overflowed therefrom. The submersion chamber18 a may have an overflow weir 20 surrounding the chamber 18 a such thatfluid may be overflowed thereto. Fluid may be continuously supplied, forexample, to the lower portion of the chamber 18 a so that fluidcontinuously overflows to the weir 20. An overflow weir 20 a (FIGS.2A-I) may be coupled to the upper separation wall 24 to aid in removingparticles from the rinsing section 26 as well as from the drying section28. High and low fluid level sensors (not shown) may be coupled to boththe chamber 18 a and the weirs 20, 20 a. In an alternative aspect, notshown, the overflow weir 20 may comprise a chamber in which theprocessing portion 10 is mounted. An exhaust line (e.g., a facilitiesexhaust line) may be coupled to the chamber (e.g., near the bottomthereof) and a drain line may be positioned along the bottom of thechamber, which may be slanted to facilitate drainage.

The rinsing section 26 may be equipped with overhead spray nozzles 30and/or submerged spray nozzles 32 each of which are adapted to directfluid to the surface of the wafer as it enters the rinsing section 26.The rinsing section 26 may, in one aspect, be used to rinse from thewafer any fluid film (e.g., surfactant) which may have been sprayed onthe wafer prior to transfer into the inventive drying apparatus 11. Ithas been found that such a surfactant spraying step prevents ahydrophobic wafer from drying during transfer to the inventive apparatus11. A surfactant spray (preferably a spray containing a lowconcentration of a surfactant such as an Alfonic surfactant) istherefore desirable prior to loading the wafer into a drying apparatusin order to prevent the formation of watermarks on the wafer. Such aninventive process may be performed in a scrubber or during wafertransfer (e.g., a wafer handler or scrubber may comprise a mechanism forwetting the substrate with surfactant either during scrubbing or as thesubstrate is removed from the scrubber or during transfer via the waferhandler).

The rinsing section 26 further includes a load port 34, which may bemerely a location through which the wafer passes as it enters therinsing section 26, or which may be an opening defined by a top wall orlid (if any) of the rinsing section 26.

Located at or near the bottom of the submersion chamber 18 a is a cradle36, adapted to receive and support a generally vertically oriented wafer(which may be slightly inclined from normal). The cradle 36 is furtheradapted to rotate from a first position in which the cradle 36 mayreceive a wafer that enters the rinsing section 26 via the load port 34,to a second position in which a wafer may be lifted from the cradle 36through an exit port 37 of the drying section 28. As the cradle 36rotates the wafer from the rinsing section 26 to the drying section 28the wafer remains submerged in the fluid.

A mechanism for rotating the cradle 36 is preferably mounted outside theprocessing portion 10 and is coupled to the cradle 36 either directly ormagnetically through a wall of the processing portion 10. In theexemplary embodiment of FIG. 1, a linkage system 38 is configured torotate the cradle 36 from the first position (within the rinsing section26) to the second position (within the drying section 28) when thelinkage is downwardly actuated, and to retract the cradle 36 from thedrying section 28 to the rinsing section 26 when the linkage system 38is upwardly actuated. An actuator 40 is shown coupled to the linkagesystem 38. The actuator 40 may be any conventional actuator such as anair cylinder or the like.

An alternative configuration for achieving cradle rotation may comprisemounting the cradle 36 on a rod that extends horizontally along thebottom of the submersion chamber 18 a so that the cradle 36 may rotateabout the rod. In such a configuration the cradle 36 may be, forexample, nearly as wide as the submersion chamber 18 a, such that amagnet may be mounted on both sides of the cradle 36, and may couplethrough the side walls of the chamber 18 a to external magnets. Theexternal magnets may be driven forward and backward by an actuator (suchas pneumatic actuator 40). To facilitate rotation of both the cradle 36and the external magnets, rollers may be mounted thereto so as tocontact and roll along the side walls of the submersion chamber 18 a.

A pair of sensors (not shown) may be coupled to the actuator 40, thelinkage system 38 and/or the cradle 36 so as to detect the first andsecond cradle positions. Further, a sensor, such as an optical sensor(not shown) may detect the presence of the wafer on the cradle 36. Oncewafer presence is detected a signal may be sent to the actuator 40 tocause the actuator 40 to rotate the cradle 36 from the first position tosecond position.

The drying section 28 may include a pusher 44 which is preferablyadapted to contact the lower edge of the wafer with minimal contactarea. Such pushers are conventionally referred to as knife-edgedpushers. The knife-edged pusher 44 may be coupled to a vertical guide(not shown) positioned along the rear wall of the drying section 28, andmay be further coupled (e.g., magnetically) to an actuator (for examplea lead screw 48 of FIG. 1, driven by a motor) which is adapted to liftand lower the pusher 44 along the guide so that the pusher 44 mayelevate a wafer from the drying section 28 and may then return to thepusher's original position below the cradle 36.

The rear wall of the drying section 28 is preferably inclined (e.g.,nine degrees) such that the pusher maintains the wafer in an inclinedposition as it is elevated from the drying section 28, so as to ensuremore repeatable wafer position than can be achieved with a non-inclined,vertical orientation.

A pair of inclined guides 46 may also be coupled to the rear wall of thedrying section 28 and positioned so as to contact the opposing edges ofthe wafer as the wafer is lifted from the cradle 36 through the dryingsection 28. Each guide 46 may be include a slot such as V or U shapedslot in which the wafer's edge is held. Alternatively each guide 46 mayinclude a beveled surface against which the wafer's edge may rest, orthe guides 46 may be angled away from the wafer so as to minimizecontact therewith.

The exit port 37 of the drying section 28 is preferably defined by a topwall or lid of the drying section 28, such that drying vapors may beexhausted therefrom (e.g., via a pump) rather than escaping into thesurrounding atmosphere. Positioned above the fluid level but below theexit port 37 are a pair of spray mechanisms 50 adapted to provide acontinuous spray of vapor across both the front and back surfaces of thewafer as the wafer is elevated from the fluid. Spray mechanisms 50 arepositioned so as to spray vapor to a meniscus that forms as the wafer islifted from the fluid. Although the spray mechanisms 50 may comprise asingle linear nozzle, or a plurality of nozzles, they preferablycomprise a tube having a line of holes formed therein (e.g., 114 holeshaving 0.005-0.007 inch diameters and being uniformly spaced along the8.5 inches that are adjacent to the wafer). Such spray tubes 50 arepreferably made of quartz or stainless steel.

Each spray tube 50 may be manually oriented so as to direct a vapor flow(e.g., IPA vapor) at a desired angle (e.g., relative to a horizontalline drawn through the center of the tubes 50 and parallel to the fluidsurface as shown in FIG. 8A). The IPA vapor flow may be directed with orwithout the aid of a flow deflector as described further with referenceto FIG. 6. A specific angle of the flow may vary depending upon thematerial of the wafer to be dried. The table listing preferred flowangles for exemplary materials is shown in FIG. 8B.

The IPA vapor flow supplied to the fluid meniscus creates a Marangoniforce that results in a downward liquid flow opposite to the wafer liftdirection. Thus, the wafer surface above the meniscus is dried.

In order to contain and exhaust the IPA vapor inside the drying section28, an exhaust manifold 51 and a nitrogen blanket manifold 54 areprovided. These manifolds may be built into a top cover 56 of the dryingsection 28, above the spray mechanisms 50. A gas flow module (not shown)coupled to spray mechanisms 50, the exhaust manifold 51 and the nitrogenblanket manifold 54 controls the IPA vapor flow rate, the exhaust rateand the nitrogen blanket flow rate. In addition, an exhaust line (notshown) may be located beneath the output portion 12 and may maintain avertical laminar flow through the output portion 12, as well as dilutingany IPA vapor that may escape from the drying section 28. The spraymechanisms 50 are preferably positioned close to the meniscus, and thenitrogen blanket manifold 54 is preferably positioned close to theunload port 37.

Wafer Processing—First Aspect

FIGS. 2A-I are schematic side elevational views which show a wafer atvarious stages as the wafer travels through the inventive apparatus 11.Referring to FIG. 2A, as a robot (such as a walking beam robot, notshown herein although disclosed in U.S. patent application Ser. No.09/558,815, filed Apr. 26, 2000, the entire disclosure of which isincorporated herein by reference) loads the wafer W into the rinsingsection 26 via the load port 34, the nozzles 30, 32 spray DI water ontoboth sides of the wafer W. The robot releases the wafer onto the cradle36, and then retracts from the rinsing section 26 to its home position,above the loadport 34. An optical sensor (not shown) detects thepresence of the wafer on the cradle 36 (FIG. 2B), and signals theactuator 40 to actuate the linkage system 38 thereby causing the cradle36 to rotate from the rinsing section 26 to the drying section 28.

The cradle 36, located at or near the bottom of the submersion tank 18a, transfers the wafer from the rinsing section 26 to the drying section28. During this transfer the wafer remains submerged in the fluid. Thusthe cradle 36 rotates from a vertical position, for receipt of thewafer, to an inclined position (e.g., 9° incline), for wafer elevationthrough the drying section 28 (FIG. 2C).

The wafer W is then lifted, via the pusher 44, toward the unload port 37with a lifting velocity profile that lifts at a process speed (e.g., 10mm/sec) from a time when the top of the wafer emerges from the tankfluid (and the drying vapor spray is initiated) until a time when thewafer's lower edge (e.g., the lower 30-40 mm of the wafer) emerges fromthe tank fluid. While the lower edge of the wafer emerges from the tankfluid and passes through the drying vapor, the wafer is lifted at aslower speed (e.g., less than 5 mm/sec, and in one embodiment about 2.5mm/sec) because the lower portion of the wafer is more difficult to dry(due to the wafer's curvature). After the entire wafer has been dried,the wafer may be lifted at a faster speed (e.g., greater than 10mm/sec.) to a transfer position. As the wafer is lifted, the wafer edgeslean by the force of gravity, on the two parallel inclined guides 46,which are submerged in the fluid.

As the wafer W is lifted out of the fluid, the pair of spray mechanisms50 (FIG. 2D) spray an IPA vapor and nitrogen mixture at the meniscusthat forms on both sides of the wafer W. The IPA vapor flow may bedirected with or without the help of a flow deflector as describedfurther with reference to FIG. 6. The specific angle of the flow mayvary depending upon the type of material on the wafer to be dried.

FIG. 8A is a schematic diagram useful in describing vapor flow angle.With reference to FIG. 8A, flow angle θ of a stream 72 of vapor/carriergas is measured relative to the water/air interface (and/or a horizontalcenter line through a nozzle tube 50) as shown. (In one embodiment, anozzle tube 50 is positioned about 0.5 inches laterally from the waferW, the flow angle is selected to be about 25°, and more preferably about23°, and the nozzle height H_(N) is selected so that the stream 72strikes the wafer W at a height H_(V) of about 3.7 mm above thewater/air interface. Other lateral spacings, flow angles, nozzle heightsH_(N) and vapor strike heights H_(V) may be employed.) A table listingpreferred flow angles (measured relative to the water/air interface) forexemplary materials is shown in FIG. 8B. Surface material refers to thematerial on a wafer that is to be dried. Dry-in or wet-in refer towhether a wafer is dry or wet prior to processing within the dryingapparatus 11. Dry-out means that a wafer is dry when removed from thedrying apparatus 11. Black Diamond® is a low k dielectric available fromApplied Materials, Inc. (e.g., carbon-doped oxide). IPA vapor flowcreates a “Marangoni” force resulting in a downward liquid flow oppositeto the wafer lift direction. Thus, the wafer surface above the meniscusis dried.

During the drying process, the IPA vapors are exhausted from theprocessing portion 10 via the exhaust manifold 51, and a flow ofnitrogen is directed across the output port 37 (via the nitrogen blanketmanifold 54) to deter IPA vapor from exiting the processing portion 10.The gas delivery module (not shown) controls the IPA vapor flow, theexhaust rate and the nitrogen blanket flow rate.

Output Portion—First Aspect

In the embodiment shown in FIGS. 1-2I the output portion 12 includes aplatform 58, adapted to rotate between two positions: a processingposition (FIG. 2E) for receiving a wafer from the drying section 28 anda FAB interface position (FIG. 2G) for outputting a wafer to a transferrobot. The processing position matches the incline at which the wafer iselevated form the drying section 28, and the processing position isgenerally horizontal. A motor or other driving mechanism coupled to theoutput portion 12 drives rotation of the platform 58.

The output portion 12 may include a catcher 60 adapted to move passivelywith the wafer W. The catcher 60 may be, for example, mounted on alinear ball slide (not shown) that has a stopper at each end. When theplatform 58 is in the processing position (e.g., vertically inclinedtoward the processing portion 10 with the same 9° incline as theinclined guides 46), the catcher 60 moves to the bottom of the linearball slide due to gravity. This low position may be detected with anoptical sensor (not shown). The catcher 60 may contact the wafer at twopoints that are separated by a distance and that may be closelytoleranced to follow the wafers circumference. Accordingly, the catcher60 may aid in precise wafer positioning.

The output portion 12 may also include a finger 62 adapted to movebetween a wafer securing position and a wafer passage position. When inthe wafer securing position the finger 62 may lock and secure the waferafter the wafer is elevated above the finger 62, thereby allowing thepusher 44 to retract, leaving the wafer held in place on the outputportion 12 by the finger 62 and the catcher 60. The finger 62 may be,for example, actuated by an air cylinder (not shown) and equipped with apair of switches (not shown) to detect the wafer securing and waferpassage positions of the finger 62. An optical sensor (not shown) mayalso be provided to sense when the wafer is at a sufficient elevationabove the finger 62 so that the finger 62 may safely assume the wafersecuring position.

Wafer Output—First Aspect

Prior to lifting the wafer W through the drying section 28, the platform58 is generally vertically inclined (e.g., with a 9° incline) (FIG. 2C).The catcher 60 is at its low position and the finger 62 is in the waferpassage position. As the wafer W exits the drying section 28 (FIG. 2D),it pushes the catcher 60 (e.g., at two points of contact) and causes thecatcher 60 to move upward therewith against gravity. The wafer W is thussecured between three points (via the pusher 44 and the catcher 60).When the pusher 44 reaches its high position, the finger 62 is actuatedto the wafer securing position so as to secure the wafer W on theplatform 58, and the pusher 44 may then retract. (The finger 62 is shownin the wafer securing position in FIG. 2E.) Because the catcher 60 movespassively with the elevating wafer W, wafer rubbing and particlegeneration during transfer into the output portion 12 may be reduced.

After the wafer W is secured on the platform 58, the platform 58 rotatesto its horizontal position (FIG. 2F). An air cylinder 64 (FIG. 1) whichmay include an adjustable stop and shock absorber (not shown) may beused to lower the platform 58 to a defined output position, for example,at an elevation where a wafer handler 66 (FIG. 2H) may extract the waferW. The finger 62 is then retracted as shown in FIG. 2H, and the waferhandler 66 picks up the wafer W to transfer it to another location(e.g., to a cassette). The platform 58 then returns to its generallyvertically inclined process position (FIG. 2I) ready to receive the nextprocessed wafer W′ as the next processing wafer W′ when it is elevatedfrom the drying section 28.

In one or more embodiments of the invention, a dedicated gas deliveryand exhaust module (not shown) may be employed to deliver isopropylalcohol (IPA) vapor, nitrogen and exhaust to the drying apparatus 11(e.g., near the spray mechanism 50). For example, clean, dry aircombined with one or more venturis (not shown) may provide the exhaust(e.g., a gas line (not shown) may supply clean, dry air to a pressureport of a venturi mounted near the unload port 42 to provide exhaust).

To provide an IPA/nitrogen flow to the spray mechanism 50, a mass flowcontroller (not shown) may provide a flow of nitrogen at a predeterminedrate to an IPA bubbler (not shown). In at least one embodiment, a 1.4liter bubbler is employed to deliver an IPA/nitrogen mixture having aconcentration of about 5% IPA. Other bubbler sizes and/or IPAconcentrations may be employed. In one particular embodiment of theinvention, a liquid mass flow controller may be employed for deliveringboth IPA and nitrogen to a vaporizer, such as a piezo-electricvaporizer; and/or an IPA concentration of about 1.5% may be employed.

In one particular embodiment of the invention, the bubbler may beequipped with three level sensors: Low, High and Hi-Hi level sensors.The first two level sensors may be used, for example, during anautomatic refill of the IPA bubbler. The latter Hi-Hi sensor may beused, for example, as a hardware interlock to prevent overfilling thebubbler. A pressurized supply vessel (not shown), such as a 1-Liter orotherwise appropriately sized vessel, may be employed to automaticallyrefill the bubbler with liquid IPA. The supply vessel may include alow-level sensor and may be automatically or manually refilled when itslow-level sensor is triggered.

A nitrogen blanket flow rate (e.g., for preventing IPA vapor fromescaping from the processing portion 10) may be controlled with a needlevalve or other suitable mechanism. Clean dry air and nitrogen blanketsupply lines may each be provided with a flow switch for safety purposes(e.g., hardware interlock flow switches that may be used to shut-off theIPA vapor supply when the exhaust or nitrogen blanket flow are lost).Pressure regulators may be used to control pressure in each supply line.

Output Portion—Second Aspect

FIGS. 3A-B are a schematic side view and a top plan view, respectively,of a second embodiment of the output portion 12 of the inventive dryingapparatus. The inventive apparatus 11 a of FIGS. 3A-B includes anenclosure 111 that surrounds the output portion 12. A translatableplatform 158 of the output portion 12 may include two or more waferreceivers 113 a, 113 b, each comprising the catcher 60 and the finger 62described with reference to FIGS. 1-2I. In this embodiment thetranslatable platform 158 is adapted to move horizontally (e.g., via alead screw, pneumatic cylinder, motor or the like), so that the waferbeing elevated from the drying portion 28 may be received by either thefirst or second wafer receiver 113 a, 113 b. In this manner waferthroughput may be maximized, as a first wafer may be held at the firstwafer receiver 113 a for pick up by a wafer handler (not shown) while asecond wafer is being output to the second wafer receiver 113 b, or viceversa.

The enclosure 111 has a first side wall 115 a which may be positionedadjacent a transfer robot (not shown). The first side wall 115 a has anopening 117 through which the transfer robot may extract wafers. Theenclosure 111 may also have an internal partition wall 115 b positionedopposite the first side wall 115 a, for dividing the enclosure 111 intotwo chambers 111 a, 111 b. The first chamber 111 a may enclose thetranslatable platform 158 with sufficient space to allow thetranslatable platform to translate back and forth so as to receive awafer at either the first or second wafer receivers 113 a-b. The secondchamber 111 b may enclose the mechanisms employed to translate thetranslatable platform 158, as well as any other moving parts(represented generally by reference numeral 159 in FIG. 3B). Such aninternal partition wall 115 b, that separates the two chambers may havea plurality of small openings 119 (FIG. 3A) that preferably cover theentire internal partition wall 115 b. When the region adjacent thetransfer robot is maintained at a higher pressure than the regionadjacent the inventive drying apparatus 11 a, air may flow laminarly inthe opening 117, across the first and second wafer receivers 113 a, 113b (parallel to the wafers' major surface as indicated by arrow F) andthrough the small openings 119 into the second chamber 111 b. The secondchamber 111 b may be exhausted via an exhaust system not shown.

In addition, an exhaust line (not shown) located beneath the outputportion 12 maintains an acceptable vertical laminar flow through theoutput portion 12, and also dilutes any IPA vapors that escape from thedrying section 28. The enclosure 111 of the output portion 12 acts as anadditional containment mechanism for preventing IPA vapor from enteringthe atmosphere surrounding the drying apparatus 11 a.

In order to allow a wafer to be output to the first wafer receiver 113 awithout blocking the processing portion 26 of the main tank 118, a frontwall 121 of the main tank 118 (i.e., the front wall of the processingportion 26) may be angled (e.g., 9°), as shown in FIG. 3A. By anglingthe front wall of the processing portion 26, the load port 34 is able tobe located far enough from the output port 37 so as to avoid blockage bythe output enclosure 111, yet the fluid volume of the processing portion10 is not increased as much as it would be if a straight front wall wereemployed. In embodiments that employ such an angled front wall thecradle 36 may be adapted to elevate to a position near the load port 34,such that a wafer handler may place a wafer on the elevated cradle 36.Such an elevating cradle 36 allows for use of a wafer handler that doesnot have the ability to rotate so as to match the angle between the loadport 34 and the bottom of the processing portion 10. The elevatablecradle 36 may be coupled to a guide located along an inside surface ofthe angled front wall, and may magnetically coupled through the frontwall to an external actuator, and thus may operate similarly to theelevatable pusher 44.

Wafer Output-Second Aspect

FIGS. 4A-I are schematic side views that show a wafer at various stagesof processing within the alternative apparatus 11 a of FIGS. 3A-B. Asshown in FIG. 4A wafer W1 is positioned on wafer receiver 113 a ofoutput platform 158 and output platform 158 is in its right-mostposition with the second wafer receiver 113 b positioned to receive thenext wafer output from the drying section 28. A wafer W2 is positionedon the submerged cradle 36 and the pusher 44 is in positioned below thecradle 36. In FIG. 4B the pusher 44 has elevated (e.g., through a slotor opening in the cradle 36) so as to lift the wafer W2 from the cradle36, and the cradle 36 has rotated back to a vertical position.

In FIG. 4C the pusher 44 has reached the elevation where the wafer W2passes through the unload port 37 and the top edge of the wafer W2contacts the catcher 60. As the wafer moves into the unload port 37 theIPA vapor spray, the nitrogen blanket and the exhaust are initiated.Also in FIG. 4C the cradle 36 has elevated and is positioned inside theload port 34 ready to receive the next incoming wafer.

As shown in FIG. 4D the first wafer W1 has been extracted from the firstwafer receiver 113 a of the enclosure 111 and the catcher 60 hasreturned to the lowered position. The second wafer W2 has been elevatedonto the second wafer receiver 113 b to an elevation above the finger62, the finger 62 has moved into positioned below the second wafer W2and the pusher 44 has lowered and is no longer supporting the secondwafer W2 which is now held between the finger 62 and the catcher 60. Athird wafer W3 has been loaded onto the cradle 36 and the cradle 36 haslowered to the bottom of the processing portion 10. Note that as thethird wafer W3 lowers through the load port 34 in may be sprayed bysubmerged nozzles 32 and/or by unsubmerged nozzles 30 (not shown).

As shown in FIG. 4E the platform 158 has moved to its left-most positionsuch that the first wafer receiver 113 a is in position to receive thenext wafer output from the drying section 28. The pusher 44 has loweredto a position below the elevation of the cradle 36 and the cradle 36 isbeginning to rotate the third wafer W from the rinsing portion 26 to thedrying portion 28.

As shown in FIG. 4F the cradle 36 has rotated to position the thirdwafer W3 in the drying portion 28 and the upper portion of the thirdwafer W3 is resting on the wafer guides 46.

As shown in FIG. 4G the pusher 44 has elevated, lifting the third waferW3 off of the cradle 36 and the cradle 36 has rotated back to a verticalposition.

As shown in FIG. 4H the pusher 44 begins to lift the third wafer W3through the IPA vapor spray and through the nitrogen blanket, to aposition where the top of the third wafer W3 contacts the catcher 60 ofthe first wafer receiver 113 a. The cradle 36 has elevated to positionitself within the load port 34, ready to receive the next incomingwafer.

As shown in FIG. 4I the second wafer W2 has been extracted from thesecond wafer receiver 113 b of the output enclosure 111 and the catcher60 has returned to its lowered position. The third wafer W3 has beenelevated onto the first wafer receiver 113 a to an elevation above thefinger 62, the finger 62 has moved into positioned below the third waferW3 and the pusher 44 has lowered and is no longer supporting the thirdwafer W3, which is now held between the finger 62 and the catcher 60. Afourth wafer W4 has been loaded onto the cradle 36 and the cradle 36 hasbeen lowered to the bottom of the rinsing portion 10. Note that as thefourth wafer W4 lowers through the load port 34 it may be sprayed bysubmerged nozzles 32 and/or by unsubmerged nozzles (not shown).

Processing Portion—Second Aspect

FIG. 5 is a side schematic view of an inventive drying apparatus 211showing only the processing portion 10 thereof. The processing portion10 is configured according to a second aspect of the present invention.Specifically, rather than a main chamber that submerges a wafer (such assubmersion chamber 18 a of FIGS. 1-2I), in the second aspect of theinvention the main chamber sprays an unsubmerged wafer with fluid bothto rinse and/or maintain the wetness of the wafer in the rinsing chamber226, and sprays the unsubmerged wafer with fluid to create the fluidmeniscus (for Marangoni drying) in the drying chamber 228. Only minorhardware differences exist between a processing portion configured forsubmersion and a processing portion configured for spray processing.

As can be seen with reference to FIG. 5, the overflow weirs 20 and 20 aof FIGS. 1-2I may be omitted. Preferably, a pair of spray nozzles 30 arepositioned to spray fluid to both the front and back surfaces of a waferas the wafer enters through the load port 34. In the embodiment of FIG.5 the separation wall 24 deters fluid spray from splashing from therinsing portion 226 into the region above the fluid nozzles provided inthe drying portion 228 (and thus deters inadvertent rewetting of a driedwafer). Within the drying portion 228, an additional fluid supplyingspray mechanism 50 a is provided below the IPA supplying spraymechanisms 50.

In operation an incoming wafer is sprayed with a fluid such as deionizedwater which may or may not include a surfactant or other cleaningchemistry such as Applied Materials' ElectraClean™ solution so as torinse and/or maintain the wetness of the wafer. As the wafer exits thedrying portion 228 the wafer is sprayed with a fluid such as deionizedwater with or without a surfactant or another cleaning agent. This exitfluid spray forms a uniform fluid meniscus across the wafer. The IPAspray mechanism 50 sprays IPA vapor to the meniscus thereby creating aMarangoni flow that dries the wafer. Note that wafer transfer within theprocessing portion 10, and wafer output to the output portion 12 may beas described with reference to FIGS. 1-4I.

Flow Deflector

The efficiency of the delivery of IPA vapor to the wafer/air/waterinterface (i.e., the meniscus) may be improved by installing a vaporflow deflector in association with each IPA vapor delivery nozzle/tube50. One such arrangement is schematically illustrated in FIG. 6. Tosimplify the drawing, a nozzle tube 50 (which may comprise the tube 50described above) and flow deflector 68 are shown only on one side of thewafer W, although in practice a nozzle tube 50 and flow detector 68 maybe provided on each side of the wafer W. Also the wafer W is shown asexiting normal to the surface of the water 76, although the wafer W mayexit the surface of the water 76 at an incline (e.g., approximately 9°from normal, although other angles may be employed).

In one embodiment of the invention, the flow deflector 68 may take theform of a two part sleeve adapted to fit around the nozzle tube 50. Afirst part 69 of the flow deflector 68 defines a wedge-shaped space 70into which a stream 72 of IPA vapor (e.g., mixed with a carrier gas suchas nitrogen) is sprayed and is designed to direct the stream 72 at aspecific angle relative to, for example, a horizontal line L drawnthrough the center of the nozzle tube 50 and parallel to the watersurface. The second part (e.g., a lower wing 74) of the flow deflector68 may dip below the surface of the water 76 to limit the volume ofwater exposed to the IPA vapor. The stream 72 of IPA vapor is preferablyangled downwardly, as illustrated in FIG. 6 so as to impinge on theinner surface 78 of the first part 69 of the flow deflector 68. Thestream 72 of IPA vapor may then be reflected (not shown) by innersurface 78 to the meniscus 80 formed at the wafer/air/water interface.In one or more embodiments, the angle between the IPA stream 72 and theinner surface 78 does not exceed 45°, although the angle of the IPAstream 72 preferably is selected so that IPA vapor strikes the meniscus80 within a desired angular range (as described below with reference toFIGS. 8A-B) and/or with a desired flow velocity to optimize IPA vapordelivery to the meniscus 80.

In one exemplary embodiment, the flow deflector 68 has a slit opening 82that may have a width of 0.05 inches and may be spaced, for example,0.10 inches above the surface of the water 76, and 0.10 inches away fromwafer W so as to efficiently deliver IPA to the meniscus 80. Other slitopening widths, distances above the surface of the water 76 and/ordistances from the wafer W may be employed. The flow deflector 68 may beaimed at an angle of 45° relative to the surface of the water 76,however other angles may be employed. Preferably the slit opening 82 isaimed so as to point just below the meniscus 80.

The flow deflector 68 serves to limit the volume of water exposed to IPAvapor, thereby reducing waste and consumption of IPA, improving dryerefficiency and performance, and reducing safety risks. In oneembodiment, the range of water volume exposed to IPA is about 0-12milliliters for a 300 mm wafer and about 0-8 milliliters for a 200 mmwafer although other ranges may be employed.

If no flow deflector 68 is employed, the stream 72 of IPA vapor mayimpinge the surface of the water 76 at an angle in the range of 22°-30°which has been found to be suitable for drying several different typesof films formed on a wafer. Other impingement angles may also beemployed. The flow deflector 68 may be constructed from a single pieceof material, or may comprise more than two parts. The flow deflector 68may be formed from stainless steel or another suitable material.

Reduced Concentration IPA Mixture

The safety and efficiency of the cleaning/drying module can be furtherimproved by reducing the concentration of IPA vapor in the IPA/carriergas mixture (e.g., to 0.2% or less) while increasing the flow rate ofthe mixture (e.g., to at least 2-3 liters per minute and preferablyabout 5 liters per minute). The increased flow rate compensates for thelow concentration of IPA and allows for highly efficient and low defectdrying with a high drying rate (e.g., 10 mm/sec, resulting in a dryingtime of 20 seconds for a 200 mm wafer assuming a constant wafer liftingspeed). FIG. 7 is a graph which plots the number of particles largerthan 0.12 microns (so called “adders” in FIG. 3) observed on wafersdried by gas (nitrogen) having various IPA concentrations and variousflow rates. Results may also vary depending on nozzle diameter, nozzlespacing from wafer surface, use of and angle of flow deflectors, etc.Experimental data shows that for a carrier gas flow rate of 5 liters perminute, the number of defects on silicon and on low k dielectriccontaining wafers does not increase when the concentration of IPA vaporis reduced from 1 percent to 0.2 percent. In one particular embodiment,an IPA/carrier gas mixture flow rate of about 15 liters per minute of1.5% concentration IPA may be employed. Such higher concentrations havebeen found to be better suited for patterned substrates. Other flowrates/concentrations may be used.

As previously noted, the wafer lifting speed may be reduced when thelower portion of the wafer W is being dried. Similarly, the IPAconcentration in the IPA/carrier gas mixture may be increased and/or theflow rate of the IPA/carrier gas mixture may be increased when the lowerportion of the wafer W is being dried. It will be understood that otherinert gases can be employed instead of nitrogen. Also, it will beunderstood that IPA can be replaced with other organic vaporsconventionally used for Marangoni drying, etc.

While the present invention has been disclosed in connection with thepreferred embodiments thereof, it should be understood that otherembodiments may fall within the spirit and scope of the invention.Particularly, it will be apparent that the inventive lifting profile,and the inventive IPA deflector can be used within any drying system,and are not limited to use within the system disclosed. Similarly, theuse of spray nozzles (underwater and/or above the water/fluid bath) torinse a substrate as it enters a rinsing tank may be employed in systemsother than those disclosed herein. A module having an angled wall withangled wafer guides for outputting a wafer in a known orientation isconsidered inventive, as is a passive output catcher. Further inventivefeatures include a method and apparatus for transferring a wafer(particularly a submerged wafer) from a first angle, to a second angle,and a module adapted to transfer the wafer from one angle to the next soas to move the wafer from alignment with an input port, to alignmentwith an output port. Accordingly, it will be understood that theembodiments described herein are merely exemplary, and an inventiveapparatus may employ one or more of the inventive features.

Some of the inventive features which may be employed individually are asfollows:

-   -   a module that combines a rinsing section and a drying section        without having the rinsed wafer surface exposed to air;    -   a rinsing section equipped with submerged and/or overhead spray        nozzles for better removal of surfactant and process tank        particles (the overhead sprays providing the most aggressive        rinsing);    -   a main tank with two sections to separate the loading and        unloading ports;    -   tubes, nozzles and/or flow deflectors that precisely deliver IPA        vapor (e.g., to the tip of the meniscus) to minimize IPA        consumption;    -   IPA spray tubes that can be precisely oriented at the best angle        for supplying IPA to the meniscus; (see U.S. Patent Application        Ser. No. 60/273,786 filed Mar. 5, 2001, titled Spray Bar, the        entire disclosure of which is incorporated herein by this        reference);    -   a friction-free guide mechanism that employs a “catcher” mounted        on the output station;    -   a cradle that simplifies the underwater wafer transfer from the        rinsing section to the drying section;    -   a variable speed pusher having a lift velocity profile;    -   slanted back wall and/or slanted front wall;    -   internal overflow weir for tanks having separate input and        output ports;    -   the enclosed output with laminar air flow;    -   a deflector that limits the surface area of fluid exposed to the        drying (e.g., IPA) vapor;    -   exhaust employing venturi for diluting organic solvent        concentration;    -   the use of a drying gas mixture having reduced concentration of        organic solvent and increased flow rate;    -   a plurality of output wafer supports for at least partially        simultaneous output from dryer and pick up by a robot; and    -   a module having a rinsing section and a section adapted for        Marangoni drying, both of which employ spray mechanisms rather        than wafer submersion.

Compared to a conventional SRD, the inventive apparatus 11 may providesuperior performance and a wider process window for drying bothhydrophobic and hydrophilic wafer surfaces. The novel drying techniquebased on the “Marangoni” principle may, in one example, leave only a 3nm thick layer for evaporation as compared to a 200 nm layer which maybe left by conventional SRDs. By combining the process module with theoutput station, the inventive apparatus may achieve a fast drying speedthat may lead to a high throughput for a wide variety of differentfilms. The rinsing section spray nozzles also may be capable of removingsurfactant that may be applied to hydrophobic wafers during scrubbingand transfer to the drying module.

It should be noted that the nitrogen blanket is merely exemplary, and ablanket of any inert gas or air or plurality of gases (including air)can be employed to form a blanket across the output port and then todeter drying vapors from escaping from the apparatus. Also, it should benoted that IPA vapor is merely exemplary, and other vapors or gases thatare miscible with the fluid (that is applied to the drying section) soas to create a Marangoni flow that dries the wafer surface may besimilarly employed. Accordingly, such vapors or gases will be referredto herein as drying gases. The terms “catcher,” “finger” and “cradle” asused herein are not intended to be limited to any specific shape orstructure, but rather refer generally to any structure that functions asdo the catcher, finger and cradle described herein.

In at least one embodiment of the invention, the wafer W is lifted, viathe pusher 44, toward the unload port 37 with a lifting velocity profilethat lifts at a process speed of about 10 mm/sec from a time when thetop of the wafer emerges from the tank fluid (and the drying vapor sprayis initiated) until a time when the wafer's lower edge (e.g., the lower30-40 mm of the wafer) emerges from the tank fluid. The wafer W isaccelerated to 10 mm/sec with an acceleration of about 293 mm/sec²,although other accelerations may be employed. While the lower edge ofthe wafer emerges from the tank fluid and passes through the dryingvapor, the wafer is lifted at a slower speed of about 2.5 mm/sec becausethe lower portion of the wafer is more difficult to dry (due to thewafer's curvature). The wafer W is decelerated to 2.5 mm/sec with adeceleration of about 293 mm/sec², although other decelerations may beemployed. After the entire wafer has been dried, the wafer may be liftedat a faster speed, greater than 10 mm/sec, such as about 70-90 mm/sec,to a transfer position. The wafer W is accelerated to 70-90 mm/sec withan acceleration of about 733 mm/sec², although other accelerations maybe employed.

In one particular embodiment of the invention, a volume of about 13liters may be employed for the chamber 18. Other sizes may be used. A DIwater (and/or surfactant and/or another cleaning chemistry) flow rate ofabout 1.3 to 1.5 liters per minute may be employed to constantly refreshthe fluid in the chamber 18. In some embodiments, a flow rate of lessthan about 1.3 liters per minute may be insufficient to adequatelyrefresh the fluid within the chamber 18 as required for Marangonidrying; and a flow rate of greater than 1.5 liters per minute maydeleteriously wet the spray mechanisms 50. A spray nozzle 30, 32 flowrate of about 2.5 liters per minute within the rinsing section 26 alsomay be employed. In at least one embodiment, DI water (and/or surfactantand/or other cleaning chemistry) flow rates into the chamber 18 of about1.3 liters per minute ±20% and spray nozzle 30, 32 flow rates of about2.5 liters per minute ±20% may be employed. After a wafer is receivedwithin the rinsing section 26, the wafer may be caused to dwell thereinfor a suitable time period (e.g., about 2 seconds in one embodiment,although other dwell times may be employed).

Accordingly, while the present invention has been disclosed inconnection with the preferred embodiments thereof, it should beunderstood that other embodiments may fall within the spirit and scopeof the invention, as defined by the following claims.

1. A method of drying a substrate comprising: lifting a substratethrough an air/fluid interface at a first rate; directing a drying vaporat the air/fluid interface during lifting of the substrate; and while aportion of the substrate remains in the air/fluid interface, reducing arate at which a remainder of the substrate is lifted through theair/fluid interface to a second rate; wherein at least one of: thedrying vapor forms an angle of about 23° with the air/fluid interface;and the second rate is about 2.5 mm/sec.
 2. The method of claim 1wherein the first rate is about 10 mm/sec and the second rate is about2.5 mm/sec.
 3. The method of claim 1 wherein the first rate is achievedby applying an acceleration to the substrate.
 4. The method of claim 3wherein the acceleration is about 293 mm/sec².
 5. The method of claim 1wherein the second rate is achieved by applying a deceleration to thesubstrate.
 6. The method of claim 5 wherein the deceleration is about293 mm/sec².
 7. The method of claim 1 further comprising: after thesubstrate is completely lifted through the air/fluid interface,increasing a rate at which the substrate is lifted above the air/fluidinterface.
 8. The method of claim 7 wherein the increased rate at whichthe substrate is lifted above the air/fluid interface is greater thanabout 10 mm/sec.
 9. The method of claim 8 wherein the increased rate atwhich the substrate is lifted above the air/fluid interface is about70-90 mm/sec.
 10. The method of claim 7 wherein the increased rate isachieved by applying an acceleration to the substrate.
 11. The method ofclaim 10 wherein the acceleration is about 733 mm/sec².
 12. The methodof claim 1 further comprising delivering both isopropyl alcohol (IPA)and nitrogen to a vaporizer using a liquid mass flow controller.
 13. Themethod of claim 1 further comprising delivering an isopropyl alcohol(IPA) concentration of about 1.5% to a vaporizer using a liquid massflow controller.
 14. A method of drying a substrate comprising: liftinga substrate through an air/fluid interface; and while lifting thesubstrate, directing an isopropyl alcohol vapor at the air/fluidinterface, wherein the isopropyl alcohol vapor is delivered using acarrier gas and the isopropyl alcohol vapor has a concentration of about1.5% within the carrier gas.
 15. The method of claim 14 wherein theisopropyl alcohol vapor/carrier gas mixture flow rate is about 15liters/minute.
 16. A method of semiconductor device manufacturing,comprising: lowering a substrate through a loadport into a processingportion of a chamber; rotating the substrate from a first orientationwherein the substrate is in line with the loadport to a secondorientation wherein the substrate is in line with an unload port,horizontally displaced from the loadport; raising the substrate out ofthe processing portion at the unload port; and at least one of:refreshing fluid in the chamber by employing a deionized water orcleaning chemistry flow rate of about 1.3 liters/minute ±20%; andspraying deionized water or the cleaning chemistry at the substrate at aflow rate of about 2.5 liters/minute ±20%.
 17. The method of claim 16wherein the volume of the chamber is about 13 liters.
 18. The method ofclaim 16 further comprising refreshing fluid in the chamber by employinga deionized water or cleaning chemistry flow rate of about 1.3 to about1.5 liters/minute.
 19. The method of claim 16 further comprisingspraying deionized water or the cleaning chemistry at the substrate at aflow rate of about 2.5 liters/minute.
 20. A method of semiconductordevice manufacturing, comprising: lowering a substrate through aloadport into a processing portion of a chamber; rotating the substratefrom a first orientation wherein the substrate is in line with theloadport to a second orientation wherein the substrate is in line withan unload port, horizontally displaced from the loadport; raising thesubstrate out of the processing portion through a rinsing section of theprocessing portion; and causing the substrate to dwell in the rinsingsection for a time period.
 21. The method of claim 20 wherein the timeperiod is about 2 seconds.